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maximum-weight-matching
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Use iterator to delete expanded blossom

This commit is contained in:
Joris van Rantwijk 2024-11-17 20:40:35 +01:00
parent 7683f891d5
commit 105679c986
1 changed files with 19 additions and 28 deletions
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47
cpp/mwmatching.h
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@ -10,6 +10,7 @@
#include <cmath>
#include <cstddef>
#include <deque>
#include <iterator>
#include <limits>
#include <list>
#include <stack>
@ -405,6 +406,9 @@ struct NonTrivialBlossom : public Blossom<WeightType>
VertexPair edge;
};
/** Iterator for this blossom in the list of non-trivial blossoms. */
typename std::list<NonTrivialBlossom>::iterator this_blossom_iterator;
/**
* List of sub-blossoms.
* Ordered by their appearance in the alternating cycle.
@ -585,10 +589,12 @@ public:
std::vector<BlossomT> trivial_blossom;
/**
* Non-trivial blossoms may be created and destroyed during
* the course of the algorithm.
* Linked list of non-trivial blossoms.
*
* These blossoms are created and destroyed during the course of the
* algorithm. Keep them in a linked list such that we can add and
* remove elements without invalidating pointers to other blossoms.
*/
// NOTE - this MUST be a list, because we delete items from it while keeping pointers to other items
std::list<NonTrivialBlossomT> nontrivial_blossom;
/**
@ -1255,8 +1261,12 @@ public:
}
// Create the new blossom object.
nontrivial_blossom.emplace_back(subblossoms, path.edges);
NonTrivialBlossomT* blossom = &nontrivial_blossom.back();
auto blossom_iterator = nontrivial_blossom.emplace(
nontrivial_blossom.end(),
subblossoms,
path.edges);
NonTrivialBlossomT* blossom = &(*blossom_iterator);
blossom->this_blossom_iterator = blossom_iterator;
// Initialize modified blossom dual to set true dual to 0.
blossom->dual_var = -2 * delta_sum;
@ -1282,21 +1292,10 @@ public:
/** Erase the specified non-trivial blossom. */
void erase_nontrivial_blossom(NonTrivialBlossomT* blossom)
{
auto blossom_it = std::find_if(
nontrivial_blossom.begin(),
nontrivial_blossom.end(),
[blossom](const NonTrivialBlossomT& b) {
return (&b == blossom);
});
assert(blossom_it != nontrivial_blossom.end());
nontrivial_blossom.erase(blossom_it);
nontrivial_blossom.erase(blossom->this_blossom_iterator);
}
/**
* Expand the specified unlabeled blossom but do not yet delete it.
*
* This function takes time O(n).
*/
/** Expand the specified unlabeled blossom but do not yet delete it. */
void expand_unlabeled_blossom_core(NonTrivialBlossomT* blossom)
{
assert(blossom->parent == nullptr);
@ -1329,22 +1328,14 @@ public:
}
}
/**
* Expand and delete the specified unlabeled blossom.
*
* This function takes time O(n).
*/
/** Expand and delete the specified unlabeled blossom. */
void expand_unlabeled_blossom(NonTrivialBlossomT* blossom)
{
expand_unlabeled_blossom_core(blossom);
erase_nontrivial_blossom(blossom);
}
/**
* Expand the specified T-blossom.
*
* This function takes time O(n).
*/
/** Expand and delete the specified T-blossom. */
void expand_t_blossom(NonTrivialBlossomT* blossom)
{
assert(blossom->parent == nullptr);